According to 

</font><p><font size="2">
<ul>
<li> <tt> ESO-327242, Integrating Instrument Performance in the Quality Control Process - X-shooter </tt>
<li> <tt> VLT-SPE-ESO-14650-3323, X-SHOOTER Technical Specification </tt>
</ul>
</font><p><font size="2">
The efficiency is specified to be 
</font><p><font size="2">
<ul>
<li> >8%  at any wavelength and 
<li> >25% in the center of all orders.
</ul>
</font><p><font size="2">
Here we monitor the wavelength averaged efficiency
in the given wavelength range.
 
<!-- 
Here we monitor the peak efficiency in the most efficient order.
-->

(The 25% efficiency is reached only in the center of a few orders. See the efficiency QC report).